The present invention relates to electronic control devices for controlling fuel to be fed to an internal combustion engine, ignition timing, secondary air flow rate for reduction of harmful exhaust gas, or emission, EGR rate, electrically heated catalyst, assisted air flow rate, gas flow intensity (swirl/tumble intensity) within cylinder and timing of inlet exhaust valves of engine, and particularly to a method of controlling these factors on the basis of signals from exhaust gas sensors provided downstream or upstream and downstream relative to a catalyst.
In the prior art, as disclosed in Japanese Patent Laid-open Gazette No. 6-257488, activation decision are made based on catalyst temperature sensors, and if activation is not made, fuel to one cylinder is cut (secondary air effect), so that the catalyst can be quickly warmed up for reduction of the emission. Also, as disclosed in Japanese Patent Laid-open Gazette No. 6-257546, ignition timing is retarded in accordance with the difference between exhaust temperatures before and after the catalyst, so that exhaust gas temperature can be increased to quickly warm up the catalyst for reduction of the emission. The catalyst deterioration judgement by signals from exhaust gas sensors before and after catalyst is described in Japanese Patent Laid-open Gazettes Nos. 5-98945, 5-98947, 5-98948, 5-98949, 5-106493, 5-106494, 5-163989, and 5-180043.
It was found that the above-given conventional methods and devices could not meet the present stringent emission regulations. Particularly when the engine is started from a cold condition at ordinary temperature, the effect of reducing the amount of the emission is not enough until the catalyst is activated from the start of engine.